Instructions for using MX Composites connecting rods

Instructions for using MX Composites connecting rods
Content
For use in single cylinder 4-stroke motorcycle engines
Page 1: Introduction
Page 2: Connecting rod to crank shaft assembly instructions
Page 3: Crank shaft to engine assembly instructions
Page 4: User manual
Introduction
Thank you for purchasing connecting rods from MX Composites!
Connecting rods are one of the most stressed parts in the engine, yet many connecting
rod failures are not caused by the connecting rod itself. Many failures are due to sheer
human errors; as improper installation, oil starvation, rough handling, overheating or
even over cycling. By carefully following the steps in these instructions you can expect
your connecting rods to function properly.
The instructions are divided in three sections. The first two sections cover different
aspects of the installation process. The last section covers important instructions for the
user of the engine equipped with an MX Composites connecting rod, i.e. the rider. Make
sure he/she reads it!
Technical support is available by sending an e-mail to support@mxcomposites.com. We
will respond within 24 hours during work week days.
/MX Composites
The MX Composites connecting rods are designed for the sole purpose of racing and shall under no
circumstances be used on public roads.
Our connecting rods are sold as performance enhancing products without any expressed or implied
warranty. You as a buyer/user assume the full responsibility for how it is used. MX Composites AB
shall not, under any circumstances, be liable for any special incidental or consequential damages,
including but not limited to damages or loss of other equipment.
We guarantee the quality of the manufacturing process and the dimensional sizes. We have no
control over customer assembly and modification of the connecting rod in the engine. There are no
further guarantees either expressed or implied by MX Composites AB or any of our agents or
representatives.
MX Composites AB reserves the right to make product improvements/changes without notice and
without incurring liability with respect to similar products previously manufactured.
The MX Composites connecting rods are patent protected.
All our products are sold under the conditions set out in our General Terms and Conditions for Sale
of Products (GTC), available at www.mxcomposites.com.
Copyright MX Composites AB 2002-2009.
MX Composites AB
Norra Stånggatan 36 SE-582 73 Linköping Phone +46 13 21 43 00 Fax +46 13 21 43 00
Registered office Linköping Reg. No. 556291-6857 VAT No SE556291-685701
www.mxcomposites.com
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Connecting rod to crank shaft assembly instructions
Before you assemble the crank shaft
Check that the connecting rod is free from scratches and other defects
Check that the connecting rod fits in piston
Check piston and crank pin tolerances
Check that the connecting rod fits in crank case and that you have enough
room to rotate crank
Always use new crank pin or one without any scratches or marks
WARNING!
Hard impacts may cause cracks that are not visible to the eye but will limit the
fatigue performance and hence the life of the connecting rod. Handle the
connecting rods with great care.
Balancing (only for skilled engine builders)
To reduce vibrations and get the best response from your connecting rod you need to
lighten the crank shaft counter weights. Easiest way to do this is to use a lathe (machine
thru turning).
Since MX Composites connecting rods generally has a thicker stem than the standard
connecting rod you need to remove material on the inside of the cranks counter weights
to make room for the connecting rod. MX Composites can provide a specific balancing
manual for each engine if demanded.
In some cases it is possible to reduce or even exclude the balance shaft/s since
vibrations are significantly reduced with MX Composites connecting rods. Make sure that
the balance shaft is only used for balancing before removing it. In some cases the
balance shaft also has other functions besides balancing.
Radial clearances
Since the connecting rod itself functions as a bearing it is very important to make sure
that the clearances are correct. Otherwise you will not have an adequate oil film built up
properly and you jeopardise the lifetime of the bearing surfaces. To make sure you have
correct clearances you should always measure the piston pin and the crank pin and
compare with the following recommendations:
Piston pin within xx.994 - xx.998 (xx=nominal dimension 15, 17, 18 or 19mm)
Crank pin within XX.992 - XX.998 (XX=nominal dimension 29, 31, 32, 33 or 34mm)
Mounting
Clean and pre lubricate every part before assembling the crank shaft. Fill the crank pin
with oil to make sure there is no air left inside the crank pin.
Axial clearance
Press the crank shaft webs to correct outer measurement, according to specific engine
model.
MX Composites AB
Norra Stånggatan 36 SE-582 73 Linköping Phone +46 13 21 43 00 Fax +46 13 21 43 00
Registered office Linköping Reg. No. 556291-6857 VAT No SE556291-685701
www.mxcomposites.com
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Crank shaft to engine assembly instructions
Engine setup recommendations
250cc engines 450cc engines
Max Piston weight: 200 g 350 g
Max rev: 15000 rpm 12000 rpm
Notice
If you use MX Composites connecting rod you can gain power by changing ignition
timing. Find out your own optimal settings in a dyno or on the track.
Lubrication
Make sure that all oil channels are working as they should and that they are clean.
Always use clean synthetic oil and fill oil pump/s and channels with oil. Before mounting
the crank shaft fill it completely with oil. It is of greatest importance that the oil channel
in the crank pin is supplying enough oil to the connecting rod slide bearing immediately
at start up. When using slide bearing solution instead of a connecting rod with roller
bearing you can remove the jet that chokes the oil flow to the crank shaft (if mounted).
Oil should be changed after 5-10 racing hours depending on use. After oil and filter
change make sure you have built up full oil pressure before starting the engine.
Alignment
To have the oil film built up correctly it is of greatest importance that the surfaces of the
connecting rod slide bearing are aligned to its respective counterpart. The easiest way to
verify this is to mount the connecting rod and measure axial clearance at piston pin and
crank pin. The connecting rod axial clearance in the piston must be larger than between
the crank webs. Also make sure that the connecting rod has enough space in the piston
during the engine cycle.
After assembly
Before starting the engine, make sure that you build up oil pressure that can supply the
bearings with new fresh oil. Do this by applying up to 50 kick-starts with the engine killswitch
pressed, or until the oil system is fully filled. Remove spark plug for easier kicking.
WARNING!
When the engine is cold, the bearing clearance is very tight. Therefore, always let
the engine warm up properly in order to achieve the correct bearing clearance
before revving the engine.
MX Composites AB
Norra Stånggatan 36 SE-582 73 Linköping Phone +46 13 21 43 00 Fax +46 13 21 43 00
Registered office Linköping Reg. No. 556291-6857 VAT No SE556291-685701
www.mxcomposites.com
3

User Manual
Before starting the engine the first time of the day always kick-start it several times with
engine kill-switch pressed. This is important since MX Composites connecting rods need
oil pressure before starting. On motorcycles with an electric starter and no kill-switch,
avoid ignition by removing the sparkplug cap.
It is essential, before every cold start, to warm up the engine on idle speed only until
reaching approx 50°C / 122 Fahrenheit. This is required since the cold clearance of the
connecting rod bearing is very tight. The bearing clearance is optimised at working
temperature and it is not until the engine has reached this temperature that the bearing
oil film can handle loads from high revs.
Recommended interval for oil change is 5-10 racing hours depending on engine usage, oil
quality and in what environment the bike is used. Find out your own interval, depending
on use.
After each oil change, make sure that there is oil in the oil channels. Do this by applying
up to 50 kick-starts with the engine kill-switch pressed, or until you are sure that the oil
system is fully filled. Remove spark plug for more effortless kicking.
Maintain other service recommendations on the engine to minimize connecting rod
problems.
MX Composites recommends a connecting rod change interval of 10 hours for 250cc
engines and 25 hours for 450cc and larger cubic engines. These recommendations are
valid for use in world top-tier motocross racing conditions.
We hope you will enjoy our product and that it may lead to many victories!
/MX Composites
MX Composites AB
Norra Stånggatan 36 SE-582 73 Linköping Phone +46 13 21 43 00 Fax +46 13 21 43 00
Registered office Linköping Reg. No. 556291-6857 VAT No SE556291-685701
www.mxcomposites.com
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